Proxy generator for Symfony's DIC

This package provides a proxy generator for Symfony's dependency injection component that generates super tiny, super simple proxies, especially when compared to Symphony's default implementation. Here are some differences:

• Can proxy final classes.
• Can only proxy classes with interfaces.
• The generated proxies are self-contained.
• The package is ~10Kb and doesn't have dependencies, other than symfony/dependency-injection of course.
• The package can be removed once the proxies have been generated.

If you're not familiar with proxy services, better have a look at Symfony's documentation before going any further.

Installation

composer require olvlvl/symfony-dependency-injection-proxy

How it works

The generator works with the following assumptions: the service we want to proxy implements an interface, and services using that service expect that interface, following the dependency inversion principle. Now, consider the following code, where an ExceptionHandler service requires a logger implementing LoggerInterface:

<?php

use Psr\Log\LoggerInterface;

class ExceptionHandler
{
    private $logger;

    public function __construct(LoggerInterface $logger)
    {
        $this->logger = $logger;
    }

    // …
}

Imagine we're using Monolog as logger, and we have an expansive stream to set up. Why waste time building the logger for every request when it's seldom used? That's when we mark our service as lazy.

The following example demonstrates how we can mark our Psr\Log\LoggerInterface service as lazy (we could use PHP code or XML just the same):

services:
  Psr\Log\LoggerInterface:
    class: Monolog\Logger
    lazy: true
    # …

The service can also use a factory:

services:
  Psr\Log\LoggerInterface:
    factory: 'LoggerFactory::build'
    lazy: true
    # …

We don't have to define our service with a class, we could use logger instead of Psr\Log\LoggerInterface just the same, except we would have to define class for the factory one.

Now let's see how to build our container.

Building the dependency injection container

The following code demonstrates how to build, compile, and dump a container:

<?php

use olvlvl\SymfonyDependencyInjectionProxy\ProxyDumper;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Dumper\PhpDumper;

$builder = new ContainerBuilder();

// …
// Here we load our config, or build the container using clever PHP calls.
// We might even have some compiler passes to add.
// …

$builder->compile();

$dumper = new PhpDumper($builder);
$dumper->setProxyDumper(new ProxyDumper());

/* @var string $containerFile */

file_put_contents($containerFile, $dumper->dump());

There you have it. We can use our container as usual and everything is awesome.

What if my lazy service implements multiple interfaces?

The basic interface resolver will have a hard time figuring out which interface to implement if a service implements many. For instance, if a service was an instance of ArrayObject the following exception would be thrown:

Don't know which interface to choose from for ArrayObject: IteratorAggregate, Traversable, ArrayAccess, Serializable, Countable.

We can specify the interface to implement using the lazy attribute:

ArrayObject:
  lazy: ArrayAccess

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Continuous Integration

The project is continuously tested by GitHub actions.

Code of Conduct

This project adheres to a Contributor Code of Conduct. By participating in this project and its community, you are expected to uphold this code.

Contributing

Please see CONTRIBUTING for details.

License

olvlvl/symfony-dependency-injection-proxy is released under the BSD-3-Clause.